com.googlecode.objectify.impl.ref.LiveRef Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of objectify Show documentation

The simplest convenient interface to the Google App Engine datastore

There is a newer version: 6.1.2

package com.googlecode.objectify.impl.ref;

import com.googlecode.objectify.Key;
import com.googlecode.objectify.Objectify;
import com.googlecode.objectify.ObjectifyService;
import com.googlecode.objectify.Ref;

import java.io.ObjectStreamException;


/**
 * Implementation of Refs which are "live" and connected to the datastore so they can fetch
 * entity values even if they have not already been loaded. This is the standard Ref implementation.
 *
 * @author Jeff Schnitzer 
 */
public class LiveRef extends Ref
{
	private static final long serialVersionUID = 1L;

	/** So that Refs can be associated with a session */
	protected transient Objectify ofy;

	/** For GWT serialization */
	protected LiveRef() {}

	/**
	 * Create a Ref based on the key
	 */
	public LiveRef(Key key) {
		this(key, ObjectifyService.ofy());
	}

	/**
	 * Create a Ref based on the key, with the specified session
	 */
	public LiveRef(Key key, Objectify ofy) {
		super(key);
		this.ofy = ofy;
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.Ref#get()
	 */
	@Override
	public T get() {
		return ofy().load().now(key());
	}

	/* (non-Javadoc)
	 * @see com.googlecode.objectify.Ref#isLoaded()
	 */
	@Override
	public boolean isLoaded() {
		return ofy().isLoaded(key());
	}

	/**
	 * Get the current objectify instance associated with this ref
	 */
	private Objectify ofy() {
		// If we have an expired transaction context, we need a new context
		if (ofy == null || (ofy.getTransaction() != null && !ofy.getTransaction().isActive()))
			ofy = ObjectifyService.ofy();

		return ofy;
	}

	/**
	 * When this serializes, write out the DeadRef version. Use the getValue() for value so that
	 * if the value is not loaded, it serializes as null.
	 */
	protected Object writeReplace() throws ObjectStreamException {
		return new DeadRef<>(key(), getValue());
	}

}